Apparatus for transferring articles through various processing sectors of a manufacturing system

ABSTRACT

A material transfer apparatus which includes a carriage whose movement is controlled along a path between specified locations thereon. The carriage includes means for dynamically indicating its present location on the path which is compared with a specified new location to provide a difference drive for moving the carriage as required. When a new location for the carriage is specified, it is dispatched under control of a cross-positioning means to approximate location of the new position whereby a sensing means on the carriage senses the carriage&#39;&#39;s approach to an indicator at the specified location, whereby control of the movement of the carriage is transferred to a fine positioning drive to accurately register the carriage with the specified location along the track.

United States Patent [191 Aronstein et al.

[ Nov. 26,1974

[ APPARATUS FOR TRANSFERRING ARTICLES THROUGH VARIOUS PROCESSING SECTORSOF A MANUFACTURING SYSTEM [73] Assignee: International Business MachinesCorporation, Armonk, NY.

[22] Filed: Dec. 29, 1972 [21] Appl. No.: 319,563

[52] US. Cl. 104/1 R, 214/16 A, 246/182 B, 318/592, 318/604, 318/666[51] Int. Cl. G05b 1/06, G05b 11/18 [58] Field of Search 318/592, 593,587, 666,

318/604; 104/1 R; 246/182 B, 187 B [56] References Cited UNITED STATESPATENTS 2,798,992 7/1957 Adler et al 318/593 3,504,362 3/1970 Feldmann246/182 B 3,570,630 3/19'71 Voight et al 318/592 3,646,890 3/1972 Snyderl04/l R 3,663,881 5/1972 Ehrenfried et al 318/666 Primary Examiner-M.Henson Wood, Jr. Assistant ExaminerGeorge H. Libman Attorney, Agent, orFirm-Henry Powers [57] ABSTRACT A material transfer apparatus whichincludes a carriage whose movement is controlled along a path betweenspecified locations thereon. The carriage includes means for dynamicallyindicating its present location on the path which is compared with aspecified new location to provide a difference drive for moving thecarriage as required. When a new location for the carriage is specified,it is dispatched under control of a cross-positioning means toapproximate location of the new position whereby a sensing means on thecarriage senses the carriage s approach to an indicator at the specifiedlocation, whereby control of the movement of the carriage is transferredto a fine positioning drive to accurately register the carriage with thespecified location along the track.

3 Claims, 19 Drawing Figures IZI MOTION Siggl CYCL PATENTE TN 26 I974sum 02 0F 13 F I G. 3

SYSTEM HANDLER CONTROL SENSOR BASED.

BASIC CONTROL SYSTEM FIG? PNENTE 243V 2 6 I974 sum 03 0F 13 l I ILCOARSE COMP 'LJDR' cofiE MATRIX I T D klA ERROR DEMO- J @124 mi TDULATOR FINE C0MP' A- 121 FIG. 5

PATENTEL, HSYZSIBM SHEET on HF 1 PATENIEb-IIGVZSIQH SHEET US UT 13 I 200I START ALL CONDITIONS NOT MET.

IS SECTOR (k) LAST SECTOR IN SEQUENCE SEND TRANSPORT TO PICK UP WORK-PIECE AT SECTOR (k) AND UNLOAD FROM SYSTEM CHECK TRANSPORTBUSY BUSY SIGALL FOLLOWING CONDITIONS ARE MET:

CHECK I EACH PROCESS SECTOR IF IF OUTPUT PEDESTAL FOR SECTOR (k) ISOCCUPIED IF NEXT SECTOR (k +1) m SEQUENCE |s OPERATIVE IF INPUT PEDESTALOF NEXT SECTOR (k +1) IN SE- QUENCE IS AVAILABLE SEKTOR (III EXIST WHEREALL CONDITIONS MET DIRECT TRANSPORT SYSTEM TO PICK UP WORK-PIECE ATOUTPUT PEDESTAL OF SECTOR (k) AND DELIVER TO INPUT PEDESTAL 0F SECTOR (k+1) TURN TRANSPORT BUSY SIGNAL ON UNTIL TRANSFER MADE IS WORK-PIECE LASTTO BE PROCESSED TURN TRANSPORT SYSTEM BUSY SIGNAL ON UNTIL WORK-PIECETRANSFER IS MADE FIG. 9

PATENTELN Z Y Y 3.850.105

SHEET O8 [IF I3 FIG. FIG. @205 I FIG. Fl 10A 7 I 7 FIG. I v w CHE-CK NOTBUSY TRANSPORT BUSY SIGNAL CHECK IF WORK-PIECE OCCUPIES AN OUTPUTSTATION OF A SELECTED SECTOR (9) UTILIZED TWICE IN A SEQUENCE OF ISECTORS OCCUPIED I IS SECTOR (II) LAST SECTOR IN SEQUENCE CHECK IF INPUTPOSITION- AVAILABLE IN NEXT SECTOR (2+ 1) WHOSE /215- NOT ADDRESS ISSPECIFIED IN SEND TRANSPORT TO AVAILABLE REGISTER OF SECTOR (II) To PICKSECTOR 1) I UP WORK-PIECE AND UNLOAD FROM SYST M F AVAILABLE I -"'2I6220 TURN TRANSPORT BUSY SIGNAL ON UNTIL TRANSFER MADE DIRECT TRANSPORTTO PICK UP WORK-PIECE AT OUTPUT POSITION OF SELECTED SELECTOR (HANDTRANSFER TO INPUT POSITION OF NEXT SECTOR I +1) WHOSE 21? ADDRESS ISSPECIFIED IN REGISTER IS OF SELECTED S,ECTOR I) WQRK-PIECE LA T TO BEPROCESSED TURN TRANSPORT BUSY INDICATOR ON UNTIL TRANSFER IS MADEPATENTEL Z N 3850.105

SHEET 07 0F I3 CHECK lF LOADING POSITIONS OFSELECTED SECTOR (it)OCCUPIED BY A WORK-PIECE cIIEcK SUCCESSIVELY FOR A FIRST SECTOR (k) INREMAINDER OF SECTORS SEQUENCE EXCLUDING m FOR FOLLOWING CONDITIONS:

" UNLOAD PoSITIoN OCCUPIED BY A WORK-PIECE SECTOR (X) IS NEXT SECTOR INSEQUENCE I LOAD POSITION OF NEXT SECTOR (k 1) 0F-REMAINDER OF SECTORSEXCLUDING (II-I IS AVAILABLE SECTOR (k 1) TO FOLLOW SECTOR (1) INSEQUENCE vN0 WORK-PIECE IN SECTOR (2) DESTIN D FOR SECTOR (k 1) ALLCONDITIONS NOT MET ALL CONDITIONS MET 224 SEND TRANSPORT TO I SECTOR.(k)& PICK UP I WORK-PIECE AND TRANSFER TO SECTOR (R) I PLACE ADDRESS OFNEXT W225 SECTOR (k 1) TO FOLLOW SECTOR I!) IN REGISTER OF SECTOR (2)TURN TRANSPORT BUSY lNDlCATOR ON'UNTIL TRANSFER IS MADE FIG. 10B AP1TTENTEL 3.850.105

SHEET 08 0F 13 CHECK SUCCESSIVELY FOR 223 A FIRST SECTOR (k) 1NREMAINDER 0F SECTORS IN SEQUENCE FOR FOLLOWING CONDITIONS: S

- HAS UNLOADING POSITION ALL OCCUPIED BY A WORK- CONDITIONS PIECE NOTMET IF A NEXT SECTOR (k 1) IS To IMMEDIATELY FOLLOW SECTOR (k) INREMAINDER 0F (SxE)CTOR SEQUENCE EXCLUDING IF sEcToR (k 1) IS OPERATIVEIF sEcToR (k 1) HASTLOADING POSITION AVAILABLE 'ALL' CONDITIONS METSECTOR (k) LAST SECTOR IN SEQUENCE ERR k%% .%K UE WORK-PIECE ANDTRANSFER SFCNKD T JE N ISEE P IE E AND To SECTQR 1) UNLOAD FROM SYSTEM lTURN TRANSPORT BUSY TURN TRANSPORT BUSY INDICATOR ON UNTIL TRANSFERlNlR/XAEOR 0N UNTIL TRANSFER MADE 0 FIG. 10C

WORK-PIECE LAST TO BE PROCESSED I I I I -24? PAIENIO IIz 3.850.105

SHEET 09 HF 13 240 IG. FIG. GET) 415 HA I HG FIG. 11A T IIC FIG. 11CHECK. v

' NOT BUSY TRANSPORT BUSY SIGNAL CHECK OUTPUT POSITION OF EACHDUPLICATED SECTORS (I) UNTIL FIRST WORK-P ECE PRESENT SIGNAL FOUND. 0RUNTIL ALL DUPLICATED SECTORS CHECKED NOT OCCUPIED IS SECTOR (1) LASTSECTOR IN I SEQUENCE 246 CHECK IF INPUT POSITION AVAILABLE IN NEXTSECTOR (1+ 1) WHOSE ADDRESS IS SPECIFIED IN REGISTER OF SECTOR (II) A245 SEND TRANSPORT-T0 SECTORIHTO'PICK UP WORK-PIECE AND UNLOAD FROMSYSTEM NOT AVAILABLE 250 AVAILABLE TURN TRANSPORT BUSY DIRECT TRANSPORTSIGNAL ON UNTIL To PICK UP WORK- TRANSFERMADE PIECE AT OUTPUT OF SECTOR(X)-& DROP A IT OFF AT INPUT OF SECTOR (1+ 1) WHOSE ADDRESS IS SPECIFIEDBY CON- TENTS OF THE SECT- OR (l) DESTINATION REGISTER IS WORK-PIECELAST TO BE PROCESSED PAIIZNILL my 25 I974 3 850 '10 5 A sum 1onr13 CHECKIF LOADING POSITION 0F DUPLICATED SECTOR (I) OCCUPIED BYA WORK-PIECEOCCUPIED CHECK SUCCESSIVELY FOR A FIRST SECTOR (k) IN REMAINDEROF'SECTOR SEQUENCE,EXCLUDING SECTOR) FOR ALL FOLLOWING CONDITIONS:

- UNLOAD Posmou OCCUPIEDBY A WORK-PIECE SECTOR-(NEXT SECTOR m SEQUENCE 0LOAD POSITION AVAILABLE IN NEXT SECTOR (k 1) OF REMAINDER OF SECTORS,EXCLUDING SECTOR I!) SECTOR (k 1) TO FOLLOW SECTOR(R)IN SEQUENCE 0 NOWORK-PIECE IN SECTOR IRIDESTINED FOR SECTOR k.+ 1)

ALL CONDITIONS NOT MET BY ANY SECTOR ALL CONDITIONS MET BY SECTOR SECTOR(k) TO PICK UP WORK-PIECE AND TRANS- SEND TRANSPORT TO FER T0 SECTOR I)I PLACE ADDRESS OF NEXT SECTOR (k 1) TO FOLLOW SECTOR") IN REGISTER OFSECTOR") TURN TRANSFER BUSY SIGNAL ON UNTIL TRANSFER MADE FIG. 11B

PAIENTELYIBYZBOII 3850.105

sum 11 OF 13 CHECK SUCCESSIVELY FoR A FIRST SECTOR (k) IN REMAINDER 0FSE CTORS IN SEQUENCE FOR FOLLOWING CONDITIONS:

0 HAS UNLOADING POSITION OCCUPIED BY A WORK-PIECE 0 IF NEXT SECTOR (k 1)IS TO IMMEDIATELY FOLLOW SECTOR (k) IN REMAINDER OF SECTORSEXCLUDINGSECTOR (2) v0 IF SECTOR (k+1) IS OPERATIVE IF SECTOR (k 1-) HASLOADING POSITION AVAILABLE,

ALL CONDITIONS NOT MET ALL CONDITIONS MET IS SECTOR (k) LAST SECTOR INSEQUENCE I YES 259 SEND TRANSPORT TO SECTOR (k) TO PICK uP SENDTRANSPORT To WORK-PIECE AND TRANs- SECTOR (k) To PICK FER T0 SECTOR(k 1) UP WORK-PIECE'AND UNLOAD FROM SYSTEM 257 I 260 I I TURN TRANSPORTBUSY 1 TURN TRANSPORT BUSY SIGNAL 0N UNTIL TRANSFER I 1 SIGNAL 0N UNTILTRANS- MADE FER MADE IS WORK-PIECE LAST-TO BE PROCESSED FIG. 1::

PATENTEQIIJVZBIEIA 3 850,105

SIIEEI FIG. 12 A BUSY CHECK TRANSPORT BUSY SIGNAL CHECK OUTPUT PEDESTALOF EACH PATTERN GENERATOR UNTIL F|RST"WAFER PRESENT SIGNAL IS FOUND ORUN IL ALL PATTERN GENERATORS HAvE- B EN CHECKED N0 WAFER PRESENT CHECKINPUT PEDESTAL OF EACH PATTERN GENERATOR SECTORS UNTIL EITHER 1. ANAVAILABLE PATTERN GENERATOR INPUT IS FOUND WAFER PRESENT AVAILABLE 2.ALL ARE CHECKED AND NONE AVAILABLE INPUT 269 AVRALTIIBELRENAL SENDTRANSPO T T 9 F IgT EL GEN WAFER AT OUT UT E OF PATTERN GENERATOR (1)AND DROP IT OFF AT INPUT PEDESTAL OF THE SECTOR WHOSE'ADDRESS ISSPECIFIED BY THECONTENTS OF THE "PATTERN GENERATOR DESTI- NATIONREGISTER" FOR PAT- TERN GENERATOR TURN TRANSPORT BUSY INDICATOR ON ANDKEEP ON UNTIL MOVE IS COMPLETED PMENTEI W28 m4 3. 850. l O 5 SHEET 13III I3 CHECK EACH PROCESS SECTOR (k) TO DETERMINE IF ALL THE FOLLOW- INGCONDITIONS ARE MET:

' OUTPUT PEDESTAL FOR PROCESS SECTOR (k) OCCUPIED BY A WAFER NO SECTOREXISTS WHERE ALL CONDITIONS ARE NET INPUT PEDESTAL FOR PROCESS SECTOR (kl) IS AVAILABLE TO RECEIVE A WAFER PROCESS SECTOR (k I 1) IS OPERATIVETHERE IS NO WAFER IN ANY I PATTERN GENERATOR SECTOR DESTINED FORPROCESSSECTOR (k l) HAS A SECTOR (k) EXISTS LAST WAFER BEEN WHERE ALLCONDITIONS PROCESSED ARE MET I DIRECT'TRANSPORT TO PICKUP WAFER ATOUTPUT PEDESTAL OF PROCESS SECTOR (k) AND DELIVER TO INPUT OF PATTERNGENERATOR III) PLACE ADDRESS OF NEXT PROCESS SECTOR (k +1) TO BE VISITED(AFTER THE PATTERN GENERATOR) INTO."DESTINATION REGISTER" FOR PATTERNGENERATOR X TURN TRANSPORT BUSYINDICATOR 276 ON AND KEEP oN UNTIL MOVEIS COMPLETED FIG. 12B

APPARATUS FOR TRANSFERRING ARTICLES THROUGH VARIOUS PROCESSING SECTORSOF A MANUFACTURING SYSTEM FIELD OF THE INVENTION BACKGROUND OF THEINVENTION This invention was developed for use in the ContinuousProcessing System disclosed and described in copending US. applicationSer. No. 329,920 filed Feb. 5, 1973 which utilizes a plurality ofsatellite functional processing operations each capable of stand-aloneoperation. This copending application is assigned to the assignee ofthis application.

As disclosed in the aforesaid copending application Ser. No. 329,920,its manufacturing system is partitioned into functional parts orsectors. Each part consists of a set of process steps designed so thatbefore and aftr which, the work product may be stored for some period oftime without degradation in product quality or expected yield. Thereason for partitioning the process this way is to allow accommodationof equipment failure and repair.

The process sectors are comprehended as standalone independentprocessing plants which accomplish a set of process steps and may have atemporary product storage unit at the output end. Work-pieces arebrought to the input port of a sector by a central trans port unit suchas that disclosed in accordance with this invention. Upon sensing thepresence of a work-piece at the input port, the sector controls causethe units to be processed through the entire sequence of steps in thatsector, and after passing, optionally, through an output buffer to anoutput port for pickup by the central transport. In accordance with wellknown techniques, measurements are provided within a sector to allowconfirmation of proper operation of tools within the sector-and in somecases where desired, to provide send-ahead information for adaptiveprocess controls to be applied in subsequent process sectors. Each ofthesectors is also envisioned to be under suitable control, either bygeneral purpose computer or a hardwired sys tem, to specify and maintainprocess parameters, and to maintain proper flow of work-pieces for thesector.

SUMMARY OF THE INVENTION The central transport system as comprehended inthis invention comprises one or more mobile work-piece carriers whichcan be commanded to pick up a workpiece from the output port of onesector and bring it to the input port of another sector. The centraltransport is operated under a control system which can be preprogrammedto specify the required sequence of sectors through which the work-pieceis to be transported so that it may undergo a prescribed sequence ofprocessing operations. Logistic control is also contemplated to beemployed to enable either the same or different work-pieces to beprocessed on a first-in first-out sequence. In operation the controlsystem enables the transport to travel to any of the input or outputpedestals of a prescribed sequence of selected sectors for pickup ordelivery of the work-piece as required by the processing schedule.

Normally, in the overall manufacturing system of copending applicationSer. No. 329,920, the work-pieces will enter the system via a loaderbuilt into the overall system or into the initial process sector whichwill perform an initial set of operations on the work-piece. Uponarrival at the output pedestal of that sector, the central transporthandler will be commanded to pickup the work-piece and deliver it to thenext (process sequence-wise) process sector, provided that the nextsector is known to be in operating condition. Upon arrival at the nextsector, the work-piece will be taken through its series of process stepswith arrival at an output pedestal for transport to the next sector inthe prescribed sequence of sectors.

Repeating this throughout the line, each work-piece is taken in sequencethrough the manufacturing steps from start to finish. The intra-sectorwork-piece flow can normally be accomplished by local controls which maybe dedicated to each sector. Each sector therefore operates as a machineindependent of the others. This mode of operation provides for fail-softoperation, independent installation and debug of process sectors,featureability of additional process sectors, and accommodation ofsector outage due to the equipment failure.

A more complete understanding of the invention may be had by referenceto the following more detailed description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammaticrepresentation in plan view of a manufacturing system embodying theprinciples of the invention of this application.

FIG. 2 is a diagrammatic representation in perspective of a transportsystem suitable for use in the manufacturing system discussed in thisinvention.

FIG. 3 is an elevational view, partly in section, of a wafer chuck whichcan be employed in association with the transport system of FIG. 2.

FIG. 4 is a schematic illustration of a control system for use with thetransport system in accordance with this invention.

FIG. 5 is a schematic illustration of a control system for a transportsystem adapted for use in a manufacturing system.

FIG. 6 is an exploded view illustrating details of a transport systemshown in the proceeding figures.

FIG. 7 is an exploded view illustrating details of a portion of atransport system to be employed for trans fer of wafers between varioussemiconductor processing sectors.

FIG. 8 is an elevational view partly in section illustrating details ofa wafer carrier incorporated in the preceeding figures.

FIGS. 9 to 12 illustrate steps of control systems for various operatingmodes employed'in the transport system of this invention.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIG. 1, amanufacturing system is shown whose overall processing operations arepartitioned, in accordance with the aforesaid copending application Ser.No. 329,920, into independent stand-alone processing stations or sectors1A to IE, each sector comprising a set of processing steps before andafter which the product may be stored for some period of time withoutdegradation in product quality or expected yield. Each of theseprocessing sectors 1A to 1F are in effect independent stand-alonemanufacturing plants which accomplish a set of processing steps, andwhich may have a temporary product storage unit at the output end.Although only six processing sctors are illustrated, it is to beunderstood that as many sectors as may be required to accommodate thetotal output of a plant, may be employed from which their preselectionand sequencing effected by means of suitable control units well in theknown art for controlling the transfer of a work-piece between thevarious sectors by a central transport unit or conveyor, generallyindicated by numeral 2.

In operation, work-pieces are brought to the input port or loadingposition of each sector by the central transport unit 2. Upon sensingthe presence of a workpiece at an input port or position, the controlsof that process sector cause the work-piece to be processed through theentire sequence of steps incorporated in that particular sector, andafter passing through the processing operation of that sector, thework-pieces are brought to the output port of that sector for pickup bythe central transport for transportation and transfer to the nextrequired sector in a prescribed sequence of work sectors specified bythe control unit regulating movement of transport 2.

The central transport 2, as disclosed in accordance with this invention,may include one or more mobile work-piece carriers which can becommanded to pick up a work-piece such as a semiconductor wafer from theoutput port or unloading position, of one sector and bring it to theinput port of any other specified sector. Normally, as further describedbelow, a servo control enables the transport to travel to any of theinput or output ports or station of the various sectors for pickup ordelivery of a work-piece as directed by the control unit.

Where the manufacturing system of this invention is adapted to themanufacture of semiconductor devices, each ofthe work sectors 1A to 1Fwill have'all the tooling required for effecting one or moresemiconductor processing operation assigned to the sector, as forexample epitaxial growth, metallization, photoresist application,photoresist pattern exposure, photoresist development, oxide etching,photoresist stripping, impurity diffusion, impurity drivein, metaletching, formation of dielectric coatings, sputtering, ion implantation,photoresist coating operations, and the like.

For purposes of illustrating a typical semiconductor manufacturingsystem, the system of FIG. 1 may be correlated to the production offield effect transistor circuits. In such applications, the system willcontain all the tooling required for producing the field effecttransistors circuits, inclusive from raw wafer through aluminum sinter.For production of field effect transistor circuits, the system willinclude an initial oxidation sector 1A; a source and drain depositionsector 18; a gate oxidation sector 1C; a pattern generating sector ID; ametallization sector 1E; and a sintering sector 1F. Except for the alignand expose units in the pattern generating sector 1D sectors, thetooling in each of the remainder sectors will be dedicated for eachprocessing series of steps. Normally, single wafers will enter the isystem at a gated rate and proceed through the sectors on a first-infirst-out basis. Preferrably, buffering will be provided at the outputports of sectors IA, 1B, 1C and IE to accommodate. any subsequentequipment unreliability. Although the buffer unit in each sector maytake any desired configuration, a typical one can be exemplified by thatdescribed in co-pending application U.S. Ser. No. 203,374 filed Nov. 30,1971, and assigned to the assignee of this application.

Wafers can be fed into the system via any suitable loader 3 built intothe initial sector, e.g. initial oxidation station 1A, which sector willgenerally perform a set of cleaning operations, growth of an oxide onthe wafer, and the application of a layer of photoresist material overthe oxide coating.

In addition, it is to be, noted that photoresist applyand-dry anddeveloped-etch-strip operations are coupled into the appropriate hotprocess sectors to enhance adhesion and cleanliness. These parts of thephotolithographic operations are distributed through a line in a mannerdesigned to maximize yield and minimize control complexity.

Align and expose apparatus is common for all levels, although thefeatureability of this system allows the use of various methods wherejustified for yield, cost, etc.

The various sectors are connected by a central transport system 2 suchas disclosed in this invention which will include a wafer handler whichcan pick up a wafer from one sector and deposit it at another. Thehandler operates on one wafer at a time for sake of mechanical andcontrol simplicity. In this specific FET processing operatio shown, thewafer will be transferred eight times during complete processing.

The processing sectors 1A to 1F are grouped around the handler assatellite stations so as to simplify the facility. Hot processingsectors are grouped in one area, aIign-and-expose sections at another,thus facilitating the installation and maintenance of specificenvironments and services required for each type of tool. For example,the aligned and expose equipment may require an air-conditionedenclosure, whereas the hot processing equipment may require exhaustventilation.

The manufacturing system includes four main buffers one at the output ofeach hot process sector, e.g. initial oxidation sector IA; source anddiffusion deposition sector IB; gate oxidation sector 1C; andmetallization sector 1E. There is normally no need for buffers at theoutput of the pattern generators unit 6 in the resist exposed sector lB,since their internal capacity is only one wafer. Provision may be madehowever for a one wafer buffer capability at the input to any of thedeveloped-etch-strip operations of the other sections to allow for thepossibility that an associated sector may go down while a wafer destinedfor it is in the align and exposed stations. As will be obvious, it isdesirable to clear the pattern generating units 6 in the expose sectorlB so that other levels can still be processed.

Temporary wafer storage buffers 4 are placed at points in the processwhere storage time does not effect yield, as for example, after theresist apply-and-dry units 5 (in work sectors IA, 1B, 1C, and 1E) whichoperation is employed prior to the aligned and exposed operation in thepattern generating units 6 of the resist expose sector 1D. In practicethe manufacturing system will be designed with a built-in over capacityof all processing sectors to allow queues to be absorbed after adown-sector is repaired. Operation of the overall manufacturing systemis asynchronous; each work sector or sub-sector to operate on a wafer assoon as it arrives, until its maximum repeat rate is reached.

The first-in first-out one-wafer at a time operation makes it relativelysimple to contain a part number mix problem. A large variety ofdifferent part numbers can be processed using a minimal productioncontrol support system to track wafers within the line. In a productionsystem of this type with a high part number mix, wafer serial and/orpart number identity can be verified prior to any of the last threealign and expose steps. This can be done during transit in the waferhandler of the central transport unit 2 by relatively simple equipmentand state-of-the-art techniques.

Illustrative of such part mix processings, is the fabrication of aninterspersed flow of different part numbers of a family of wafers inwhich the processing parameters of the various processing sectors, withthe exclusion of the pattern generators 6, are substantially the same.In this respect, personalization of the various part numbers is affectedby suitable reading of the wafer serial and/or part number, to selectthe appropriate pattern or mask to be employed by a pattern generator 6for exposing the resist coated wafers at their various levels ofprocessing corresponding to the particular part number of the productmix flow.

The central transport system 2 as disclosed herein can comprise one ormore mobile wafer carriers 7 which will include a wafer pickup andrelease mechanism 8 on a carriage 9 which travels along a guide rail 10as illustrated in FIGQZ. As shown in the drawing pedestals or columns 11support the guide rail 10 above the load and unload pedestals of thevarious process sectors or stations. In general, input and outputpositions of all process sectors are on a common line below the guiderail. Wafers are picked up, carried, and deposited in a horizontalface-up position.

' Wafer pickup can be accomplished by a version of the Bernoulli probe,such as shown in FIG. 3 as part of the wafer lifter mechanism, orpreferably the wafer pick-up can be of the type shown and described withreference to FIG. 8 herein. In one form the wafer pickup 12 illustratedin FIG. 3 comprises a base plate formed with a plurality of peripheralapertures 14 through which are mounted a radial assortmentofflexiblevtubing 17 connected with a vacuum manifold 15 coupled to asource of pressure at the vacuum inputs l6. Mounted about each of thetubings 17 is a yoke unit 18 in which is secured a light leaf spring 19which is anchored at its other end in the body portion 20 to bias thefree ends of the tube 17 uniformly out of the front face of supportplate 14 so as to secure a wafer thereto when the vacuum is turned on atan appropriate time. Extending through the body portions 20 is an airpassage 21 connected to source of positive gas pressure to reject asource or steam of gas out of the nozzle 22 to provide a Bernoullieffect which will raise a wafer 23 against the open ends of tube 17 forsecuring a wafer thereto under pressure. As it will be noted, the tubes17 are spaced about base plate 24 for engagement about correspondingperipheral portions of wafer 23.

In general the carriage assembly 9 comprises the pickup head 8, aZ-motion drive motor 7, a drive motor 25 for driving a pinion gear 120along a rack 26 secured on the upper surface of support rail 10. Ingeneral, information for driving or for controlling the movement of thetransport system 2 will be transmitted by means of a service cable 27extending from a control unit which specifies the selectedsequence ofprocess sectors through which the wafer is to be sequenced, whichsectors are available for wafer input, senses the presence of a waferavailable for pickup at the output of a sector, senses carriage status(availability to pickup a wafer), and senses carriage location. Morespecific details of the transport are described below.

As indicated previously, the process sectors or stations are configuredto accomplish a set of process steps which can be done in a rapidsequence to meet high-yield objective and for this purpose each sectorcan be optimized to obtain such result. For this reason, the apparatuswithin each sector is selected on the basis of highest yield potential.

Each sector will also contain adequate timing, motion, and parametercontrols to allow for debug and system operation and maintenance.Additionally, an interface can be provided to a control system for datacollection, wafer tracking, and where appropriate, overriding computercontrol of critical parameters in accordance with well establishedtechniques.

Although the wafer transfer system 2 can take various configuration, thepreferred form is in accordance with the invention that is disclosedherein. As described in this application, a schematic overview of thisparts handling system is illustrated in FIG. 4. As shown, the centraltransport system 2 will comprise one or more mobile wafer carriers 9mounted on a rail 10, with the carrier connected by service cable 27 toa handler control system 111. As indicated above, the central transportsystem is connected to the control system by a cable, and a series ofinput and output pedestals of each processing sector or station, asshown in FIG. 4, are distributed along the rail 10 of the transportsystem. Each of the pedestals associated with the sectors has a PARTPRESENCE sensor (e.g. photosensor) which sends an electrical signal to asensor based control system 112, which will perform various functions inthe operation of the manufacturing system of this invention, onefunction of which is to control the movement of parts or work-piecesfrom pedestal to pedestal of the various processing sectors or stationsthrough which the work-piece is sequenced.

The control system 112 will periodically test for a part 113 present ata pedestal. When one is present at an output or unload pedestal, aseries of decisions is made before a move is initiated. The designationoutput might refer to the output or pickup point of a tool or collectionof tools. The control system 112 decides which tool a work-piece or part113 should be moved to next, senses that the input" pedestal or port ofthe next tool is available (e. g. no part is currently on it) and sendsin an address to handler control system 111: The address sent is that ofthe output" pedestal containng the part 113 to be moved. The handlercontrol system accepts this address and dispatches the carriage 9, fromwherever it might currently be located, to the output- /input pedestaladdress. The carriage proceeds 'to this address under control of a servosubsystem (described below). When the move has been completed and thehandler 9 has picked up the part, the handler control system 111 sends amovement complete signal back to the control system 112 to inform itthat the handler control system is now ready to move to the new address.The control system 112 recalls the input" pedestal address to which thispart must be moved and sends this address to the handler control system111, which then proceeds to move the carriage or handler 9 to thespecified address. At the completion of this movement, the work-piece113 will then be transferred to the input of the next work sector orstation required in a preselected sequence sector. After this movement,the handler control system 111 again sends a movement complete signal tothe control system 112, which now can resume its periodic testing ofoutput" pedestals for other parts to be moved.

The wafer handler 9 of the central transport system 2 is comprised of acarriage 7 on which are mounted the main drive motor 25, a vernier orfine positioning motor 12, a coarse positioning potentiometer 115, afine position sensor 120, a clutch brake 116 and a Z- axis mechanism 117for raising and lowering the wafer pickup chuck 8. Normally, thecarriage will traverse the central transit rail 1 on support rollers 118and guide rollers 119 with a positive drive through a pinion gear 120meshing with a gear rack 26. The fine position sensor will comprise amagnetic proximity detector 120 of the E-transformer type which islocated on the wafer carrier 9 with the actuating bar 121 mounted on therail at each stopping address of the various processing sectors orstations. This establishes a final stopping point for the carriage 9 inconjunction with minimizing drift and calibration problems andeliminating any type of mechanical contact at the stopping address. Aservo demodulator 122 is employed to convert the AC signal from thedelector to DC for the use by the fine positioning or vernier motor 12.

The wafer handler 9 is controlled by a two-mode servo mechanism system.This servo mechanism system is shown schematically in FIG. 5. The highspeed or coarse position mode utilizes a typical direct current servowith a potentiometer feedback. The low speed or fine position modeutilizes a modified DC servo with a non-contact position sensor 120which detects a fixed segment on the rail at the stopping point and onwhich is mounted on the actuating bar 121. There is one fine positionsensor 120 on carriage 9 and one fixed actuating bar sesgment 121 ateach pedestal location or stopping address of the various processingsectors or stations.

Also, included on the carriage are the two servo motors, e.g. the mainmotor drive 25 and the fine positioning or vernier motor 12, the coarseposition potentiometer 115- and the Z-motion mechanism 117. Alsoincluded in the wafer carriage 9 is the gear and drive mechanism (seeFIG. 10) with which is associated electro-mechanical clutch 123 and anelectro-mechanical brake 116. The handler controller includes a servoamplifier 123, an address matrix 124 which serves as a digital to analogconverter, a coarse position summing amplifier 125, a fine positiondemodulator 122 which converts a signal from the fine position sensorfrom AC to DC; and also included are a pair of voltage comparators, e.g.a coarse comparator 126 and a fine comparator 127, plus all requiredlogic and power supplies to run the controller and the carriage.

With reference to FIG. 5, the operation of the system may be consideredrelative to the status of the system prior to making a move. At thispoint in time, the carriage 9 will normally be positioned over someinput or output pedestal along the rail 10, the identification of whichis of no moment for purposes of this consideration. At this time thebrake 116 will be on, locking the carriage 9 to the rail 10. To initiatea movement to a different pedestal, a digital address is placed at theinput of the address matrix 124. This generates a voltage or coarseaddress signal at the positive input of the coarse position summingamplifier 125. The current position of the carriage 9 is represented bythe voltage from the coarse position potentiometer 115, which appears atthe negative input of the summing amplifier 125. The output ofthesumming amplifier 125 is a voltage which is proportional to the distanceto be moved and of the proper polarity to drive the carriage 9 in theproper direction. At the onset, this error signal exceeds the magnitudeof permissive tolerance EC signal level and the coarse comparatorsswitches the control into the coarse mode. This switch" connects thecoarse error signal to the input of the servo amplifier 123 and connectsthe output of the servo amplifier 123 to the coarse drive motor 25.

Simultaneously, brake 116 and clutch 123 are released. The brake releaseallows the carriage 9 to move with respect to rail 10, and the clutchrelease disengages the fine or vernier motor 12, allowing the coarsemotor 25 to drive the carriage. The acceleration of the carriage drivewill be determined by the maximum output current of this servo amplifier123. The final running speed will be determined by the maximum outputvoltage of this servo amplifier. The gain of the servo amplifier willnormally be set sufficiently high so that the amplifier operates ineither voltage or current limit until the carriage 9 has traveled to theapproximate position of its stopping address. When this point isreached, the value of the coarse error signal will be low enough toallow the servo amplifier 123 to operate in its linear region. Since themass of the carriage 9 will be quite large and the rolling frictionsmall, braking will be required to decelerate it within the remainingdistance of travel. This is done electrically by the servo amplifier123. As the carriage 9 approaches its stopping address, the outputvoltage of the servo amplifier 123 will decrease faster than the backEMF of the coarse motor 25. This will cause the current to reversedirection and consequently, the torque at the shaft of the motor willreverse, causing the required braking. The amount of reverse current iscontrolled by the amplifier and hence the rate of the deceleration isalso controlled.

As the carriage 9 moves towards the stopping address, the coarse errorsignal decreases proportionately until it is less than the coarsetolerance ABC. The coarsse comparator 126 detects this level andswitches to the fine positioning mode. The compare level, AEC, will beselected so that the carriage 9 will have entered the range of the finepositioning sensor 120. This null position will be sensed at the outputof the demodulator by a second fine comparator 127. When this outputbecomes less than a preset fine tolerance AEF signal level, the carriage9 will have been driven to within the re quired tolerance of thestopping address, and the comparator 127 will switch to the stop mode.This switch includes turning on the brake 116 to lock the carriage 9 inthe position on rail 10, and sending a pulse'to the Z-axis" motionmechanism to either pick up or put down a part which may be carried onthe chuck 8. When the Z motion is completed, a switch closure on themechanism will signal the control unit that the carriage move has beencompleted.

As indicated above, the Z-motion mechanism 117 is I employed toload/unload work-pieces to and from input/output pedestals onthe variousprocessing sectors P 1??!19953-5;ll lfe.

After the work handler or carriage 9 is positioned over the appropriateinput/output station it is ready to start its load/unload cycle. When awork-piece is in the holder, it will be unloaded onto an input or loadpedestal of the next specified processing sector or station; and whenthe carrier is not transporting a work-piece, it will be directed to anoutput pedestal of a sector and the work-piece at that point will bepicked up by the handler for transfer to another processing sector orstation.

When the carriage is positioned and stationary at its specified address,the loading/unloading cycle is started by command to drive motor 143which is connected to a one revolution clutch 142. The Z-motionmechanism is actuated during one revolution of the output shaft of drivemotor 143 through a gear set 147 serving as an input to the cam index147A which will revolve twice during the cycle as a result of the two toone ratio of gearing set 147. The output crank 148 will make an up anddown motion with appropriate dwell on the bottom of the stroke, andsince the crank 148 is attached in slot 150 of slide block 151, thewafer chuck will be moved up and down on slide rods 149 so to place orremove a work-piece from the input or output pedestal station.

Meanwhile during the up and down stroke, holder fingers 160 (see FIG. 7)are actuated to open or to close position as the case might be.Concurrently, the cams and 146 make only one half of a revolution duringthe cycle due to a one to tworatio of gear set 144. Thus, the fingers160 on holder or chuck 8 are opened or closed during the cycle. Thetiming of cams 145 and 146 will be such that the finger actuation isbehind the down movement at theextreme bottom portion of the slide 150to give time delay for actuation of the fingers during the dwell of theindexer.

Actuation of the fingers 160 is effected by means of a rod -having anenlarged drive shoulder section 171 mounted within slots 172 of fingers160 which will, as a result, be forced open and closed by movement ofthe cam rod 170 up and down. Secured about cam rod 170 is a piston 173which will travel up and down within va bore 174 of cylinder block 175.The upper portion of the cylinder block is provided with a cylinder head176 having a bore for reciprocation of the cam rod 170 therethrough.Secured at an upper portion of cam rod 170 is a retaining flange 177 fora return spring 178 contained against the cylinder head 176. An inletfor gas pressure into the cylinder space 179 is formed by a bore 180whose outlet 181 is connected to a suitable source of gas pressure.Mounted on the cylinder block 175 is a bracket 182 having on which issecured an extending mounting rod 183 attached at its other end to aplate 184 which in turn is mounted to a slide block 185. If desired, awork-piece mounting rod 183 attached at its other end to a plate 184which in turn is mounted to a slide block 185. If desired, a workpiece,such as a wafer, can be further supported on the inwardly extendingportions of fingers 160 by provision of vacuum holes into each holderfinger. Actuation of vacuum to the fingers and comming the fingersopened and closed is means of a cam 145 and 146 which suitably activatefluid valves 145A and 146A. The camming indexer 147 will comprise anindexer input 147A and an indexer output 1473. Also in the preferredmode the chuck 8 will include an environmental enclosure or cover 185through which an environmental atmosphere can be injected via hose 186.

Normally, a plant erected to incorporate the manufacturing system ofthis mention will be under computer control, and be incorporated in thebasic control system unit 112 of FIG. 4. In such an environment, anyassociated memory of the computer, e.g. tape or disc, may have enteredinto it a plurality of part programs consisting of a series ofinstructions specifying the required operations of work-piece, togetherwith the necessary process parameters within each processing sector aswell as means for self-adaptive automatic processing within the sectoror between processing sectors. In conjunction with specifying therequired sequence of processing operations to be performed, the programwill also specify a corresponding preselection of the sequence ofprocessing sectors through which a workpiece must be processed to effectits desired total processing. Each part program will be identified by apart number, or other suitable codes which uniquely associates theseries of operation to be performed with a particular part on which theoperations are to be performed. In addition, the control system willinclude provision for the storage of additional part programs for a newpart number, or modification of existing part programs as required forexisting part numbers.

To initiate operation, the control system is informed e.g. by anoperator at a console or terminal of the part number to be processedwhereby the file of the computer memory will be searched for the partprogram, associated with the part number, for transmittal to the controlsystem. After transmittal of the part program to the control system thefunctional units of each processing sector will be activated to thestatus required for processing of the workpiece. In conjunction with themain control system, each sector can be provided with its own individualcontrol for setting process parameters and for wafer flow within thesector. A sector may be operated as a stand-alone machine such that onecan present a wafer at the input pedestal, and it will be processedthrough to the output pedestal, the sector controls providing forrouting of the wafer through the process tubes in that sector as well ascontrol of parameters within the sector, as for example, temperature,gas flows, etc. such as employed for semiconductor processing.

Each sector control system can communicate with the main control system,which can monitor sector-tosector work-piece flow, provide adaptivecontrol functions, and record required parametric data. In addition, themain control unit can communicate with those factory systems whichsupport the functions of production control, design and processautomation, quality testing, etc.

The control of process parameters, e.g., temperatures, flows, etc., canbe accomplished by standard analog or digital means. Selection of theparticular method of control will normally be made on a basis ofprecision, reliability, cost, compatibility with the unit beingcontrolled and other standard engineering considerations. In some cases,it may be desirable to have the main control system set the parameterlevels. .For example, in a semiconductor processing system, the settingof an etch time can be made a function of the thickness of materialmeasured in the previous sector on the wafer. Override motor control mayalso be provided for parameter setting by the main control unit in suchcases. In the absence of a signal from the main control unit, the localcontrol (e.g. each sector) must refer to its nominal set point or remainat the set point indicated by the last available main control unitsignal whichever is appropriate for the particular parameter ofinterest. Monitoring of functions, is also comprehended to insure thatequipment failure will not result in catastrophic mishap and also toinsure that the process is in control and product is made withinallowable specification. The monitoring of process parameters can bedone by the main control unit, using redundant sensing elements builtinto each sector, such that the same sensors will not be used forcontrol of the parameter and for monitoring the parameter. Also, themain control unit can compare critical parameter values againstpredetermined limits and when required, take appropriate action inaccordance with techniques well known in the art, for notifyingmaintenance and inhibiting further entry of work-pieces to that sector.

At critical work-piece transfer points within a sector, a signal can begenerated for the main control unit to enable it to monitor progress ofwork-pieces through the sector and to track individual work-pieces forpart number control and for correlation of parameter and measurementdata with individual work-piece final test results.

As indicated above among the important functions of such a control unitis for logistic control of work-pieces through the various sectors ofthe overall manufacturing system, e.g. specifying the manner in whichthe work-pieces are indexed through a specified sequence of selectedprocessing sectors. A preferred approach for such logistic control ofprescribed sequencing of work-pieces through the sectors is thatdisclosed and described in copending application U.S. Ser. No. 329,494filed Feb. 5, 1973 and also assigned to the assignee of thisapplication. The invention disclosed in this copending applicationcomprehends various modes of operating manufacturing system of atransport system in the'aforedescribed copending application Ser. No.329,920.

In all modes of sequencing a work-piece, the logic of the control systemis based on a fixed routing of the work-piece through all processingsectors for each part number of the work-pieces involved. Also, thelogic of the movement of work-pieces between sectors is based on knowingthestatus of the input and output pedestals or positions of eachprocessing sector. Therefore, the logic depends on an output pedestalstatus indicator for each sector and an input pedestal status indicatorfor each of these sectors. Also, the logic requires a transport systemstatus indicator to reflect the units availability for movement of thework-pieces through the various processing sectors. Thus, the logic ofthe various modes of sequencing wafers is based on a continuous pollingof the indicators, in such a way as to meet an objective of trying tokeep each processing sectors input pedestal occupied by a wafer. Thefirst,

mode comprehended in the aforesaid copending application U.S. Ser. No.329,494 relates to the sequencing of work-pieces through a preselectedsequence of processing sectors all of which are dedicated to a specificportion of the overall process, and an individual workpiece will onlyvisit such a sector only one time. FIG. 9 illustrates an outline ofsteps present in this mode of operation. Referring to FIG. 9, the firstSTART Step 200 is employed to initiate the control system for sequencingthe work-pieces through the processing sectors. On initiation, thesystem proceeds to Step20l to determine if the transport system 2 ispresently in the process of transferring a workpiece between sectors. Ifa negative determination is found for any one of those foregoingconditions (eg all conditions not met) at all sectors, the system at thelast sector (K n) will proceed to Step 208 to determine if the output orunload pedestal of this last sector (K n) is occupied by a finishedwork-piece. On a negative determination in Step 208, the system willreturn to Step 201.

Conversely, if the determination of Step 208 is positive, indicatingthat the output position of the last sector (K+n) is occupied by afinished work-piece which can be unloaded out of the processing line,the control system as indicated in Step 209, will dispatch the transportsystem to output pedestal of the last sector (K+n) to pick up thework-piece and to unload it from the system, while as Step 210concurrently, turning on the transport units busy indicator on until themove is made. On completion of the move, the system will proceed to Step211 to determine if the last scheduled work-piece has been proceedede.g. no further workpieces are to be processed. On a positivedetermination, the system will proceed to stop Step 212 to terminatefurther operation of the control system; and if a negative determinationis made, the control system will return to Step 201 sectors. If apositive determination is made to the effect that transport system is atthat time transporting a work-piece, the determination of Step 201 isrepeated as necessary until the transport unit is found to be free. 7

If the transport system is found to be available, the control systemwill proceed to Step 202 for successively checking each of theprocessing sectors until a sector is found meeting all three of thefollowing condimom:

I. If the output position pedestal for a sector (K) being checked isoccupied by a work-piece;

2. If the next succeeding sector (K l) in the prescribed sequence ofsectors is operative; and

3. If theinput pedestal of this next sector (K l) in the sequence isavailable.

If a sector (K) is found which first meets all of the signal will beturned off, with the control system profor repeating the determinationceeding to Step 201 therein.

A second mode of operation comprehended in the said copendingapplication U.S. Ser. No. 329,494 is directed to the transfer of awork-piece to a plurality of processing sectors wherein is includedselected pro-

1. Apparatus for positioning a moveable member comprising: A. trackmeans for controlling the movement of said moveable member along apredetermined path; B. means for reversibly driving said member alongsaid path through and to any one of a plurality of locations thereon; C.means for continuously generating a first analog signal representing thelocation of said member along any point of said path including any pointbetween and at said locations; D. means for generating a second analogsignal corresponding to a specified new location for said member alongsaid path; E. means for continuously generating a difference signal,from said first and second signals representative of the distance anddirection of said member from and to, respectively, said new locationwith said drive means responsive thereto for moving said member to saidnew location; F. means to stop said member at said desired location; G.wherein said second signal generating means comprises an address circuitmeans for generating a digitally coded electrical signal specifying asaid desired new location for said member, and for converting saiddigitally coded electrical signal to a representative said second analogsignal; H. wherein said first signal generating means comprises a motionsensing means coupled to said drive means for continuously producingsaid first analog signal representing the position of said member alongany point of said path; I. whereiN said summing means comprises asumming amplifier for generating said difference signal amplifier; andJ. including means for generating a tolerance signal representingpermissible deviation of said member from coincidence with a saiddesired location; means for comparing said difference signal with saidtolerance signal and generating a coincidence signal therebetween; andmeans responsive to said coincidence signal to activate said stoppingmeans; K. wherein said activating means comprises means for generating afine tolerance signal representing a smaller permissible deviation ofsaid member from coincidence with said specified location; positionrepresenting stop means comprising a magnet at each said desiredlocation along said path; means on said member for sensing said magnetand generate a fine difference signal therebetween; means for comparingsaid fine difference signal with said fine signal and on coincidencetherebetween generating a stop signal for said drive means.
 2. Theapparatus of claim 1 wherein said drive means comprises a coarse motormeans responsive to the first said difference signal of said summingamplifier and a fine motor means responsive to said fine differencesignal; a drive mechanism for said reversible driving of said member; aclutch means for interchangeably engaging said drive mechanism betweensaid coarse and fine motor means in response, respectively to theabsence and presence of said coincidence signal; and brake means forstopping said member in response to said stop signal.
 3. The apparatusof claim 2 wherein said drive mechanism includes a pinion meshed with arack on said track means.